The present invention relates to a wiring film having less dielectric loss, so as to be able to cope with high frequency signals, and to a low dielectric loss tangent film used therefor.
In recent years, the signal bands of information communication equipment, such as PHS or portable telephones, and the CPU clock times of computers, have reached the GHz level, and the working frequency in electronic devices has become higher. The dielectric loss of electric signals is in proportion to the product of the square root of a specific dielectric constant, the dielectric loss tangent of an insulator forming a circuit and the frequency of the signals being used. Accordingly, as the frequency of the signals being used is made higher, the dielectric loss increases. Since the dielectric loss attenuates electric signals, thereby to deteriorate the reliability of the signals, it is necessary to select insulators from materials having a low dielectric loss constant and a low dielectric tangent so as to suppress the loss. In order to lower the dielectric constant and lower the dielectric loss tangent of an insulator, it is effective to remove polar groups in the molecular structure; and, for this purpose, the use of fluoro resin, curable polyolefin, cyanate ester type resin, curable polyphenylene oxide, allyl modified polyphenylene ether, or divinyl benzene or divinyl naphthalene-modified polyether imide have been proposed. For example, fluoro resins, typically represented by polytetrafluoroethylene (PTFE), have a low dielectric constant and a low dielectric loss tangent, and so they are typically used for substrate materials handling high frequency signals. While, on the other hand, various non-fluoro resins having a low dielectric constant and a low dielectric loss tangent which are soluble to organic solvents and can be handled easily, have also been studied. They include various materials, for example, dienic polymers, such as polybutadiene impregnated into glass cloth and cured by peroxides, as disclosed in Japanese Patent Laid-open No. 8-208856; cyclic polyolefins provided with curability by introducing epoxy groups into a norbornene series addition type polymer, as disclosed in Japanese Patent Laid-open No. 10-158337; cyanate ester, dienic polymer and epoxy resin heated into the B stage, as disclosed in Japanese Patent Laid-open No. 11-124491; modified resins, including polyphenylene oxide, dienic polymer and triallyl isocyanate, as disclosed in Japanese Patent Laid-open No. 9-118759; resin compositions comprising, for example, allylated polyphenylene ether and triallylisocyanate, as disclosed in Japanese Patent Laid-Open Hei 9-246429; polyetherimide alloyed with styrene, divinyl benzene or divinyl naphthalene, as disclosed in Japanese Patent Laid-open No. 5-156159; and resin compositions comprising, for example, hydroquinone bis(vinyl benzyl) ether and novolac phenol resin synthesized from dihydroxy compound and chloromethyl styrene by Williamson synthesis, as disclosed in Japanese Patent Laid-open No. 5-78552.
However, even the materials of low dielectric constant and low dielectric loss tangent, as described above, do not have sufficient dielectric characteristics to cope with the high frequency equipment which is expected in the future.